Because of the advantages offered by electroplating, such as cost efficiency, ease of fabrication and scalability, shape controllability, and the ability to integrate with other micro-electro-mechanical system (MEMS) processes, the electrodeposition of cobalt-platinum (CoPt) permanent magnets has been widely studied as an attractive and practical fabrication technique for various MEMS applications.
Because most MEMS are built on substrates, it is also desirable to have a process to integrate CoPt permanent magnets onto substrates. Generally, however, a silicon substrate, for example, is not electrically conductive enough to use electroplating to form CoPt permanent magnets on the Si substrate, or there may be dielectric layers on the Si substrate which prevent the use of electroplating processes. Therefore, it is necessary and customary to use an electrically conductive seed layer (e.g., a copper (Cu) seed layer) onto which electroplated CoPt films can be deposited.
Once formed, CoPt layers require a high-temperature (e.g., between about 500-750° C.) heat treatment, such as an annealing treatment or step, to induce a phase transition for desirable magnetic properties. Unfortunately, this high temperature step creates a variety of challenges for the integration of CoPt permanent magnets on substrates.
The drawings illustrate only example embodiments and are therefore not to be considered limiting of the scope of the embodiments described herein, as other embodiments are within the scope of this disclosure. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey certain principles. In the drawings, similar reference numerals between figures designate like or corresponding, but not necessarily the same, elements.